Air conveyors are commonly used to convey empty plastic bottles. The bottles are supported between a pair of opposing guides (known as neck guides) by a ring-like flange located between the containers shoulder and the threaded part of the neck. Air is blown in the direction in which the bottles are to be conveyed, usually at the level of the neck, less commonly on the bottle's body. This type of conveyor eliminates the problems associated with container stability. Another advantage is the high speed at which the bottles may be conveyed.
One drawback with such air conveyors arises when bottles with different neck diameters need to be conveyed on the same conveyor. On one hand, if the distance between the guides is too great the diameter of the flange will not be sufficient to hold the bottles in the conveyor. On the other hand, if the distance between the neck guides is too small the bottles will jam.
In order to address the above drawbacks, the prior art reveals conveyor guide systems which increase or decrease the distance between neck guides automatically allowing for different sized bottle necks, typically by means of pneumatic pistons which are fastened to the guides. However, one drawback with these systems is that they typically operate with the piston rod of the pneumatic piston either extended or retracted, thereby only accommodating two sizes of bottle necks. Additionally, fine tuning of the distance between neck guides may be carried out by means of an adjustment screw, but once set no further adjustment is generally possible during operation of the conveyor. This in turn means, for example, that small variations in bottle neck size of bottles of the same capacity, which typically arise between consecutive batches of a production process or bottles from different manufacturers, cannot be taken into account.